The Northern Lights glow green in a spectacular light show above a field of trees frozen solid with snow. (Photo by Jaak Sarv/Solent News & Photo Agency)

A woman selling souvenirs walks through Kuta beach in Bali June 5, 2008. Indonesia is expected to report tourist arrivals in December this week. (Photo by Murdani Usman/Reuters)

Potters colour earthen lamps at a workshop ahead of the Hindu festival of Diwali in Amritsar October 15, 2014. Earthen lamps are sold in large numbers during Diwali, the annual Hindu festival of lights, as people use them to decorate their homes. (Photo by Munish Sharma/Reuters)

A Santa Claus puppet holding a Christmas tree is pictured against the sun in Berlin November 23, 2014. (Photo by Hannibal Hanschke/Reuters)

People ride a Ferris wheel as fireworks illuminate the sky over Edinburgh, Scotland. (Photo by David Cheskin/Press Association)

A woman looks out from her stall selling traditional garments and textiles at a market in Ashgabat February 8, 2012. (Photo by Aman Mehinli/Reuters)

“Don't Leave Any Food On Your Plate”. The giraffes at Nairobi's Giraffe Manor are totally at home with humans. They will eat out of your hand, or even off your plate. Photo location: Giraffe Manor, Nairobi, Kenya. (Photo and caption by Gavin Werbeloff/National Geographic Photo Contest)

In this October 15, 2014 file photo, Katsu Nakamura, sky division manager for Yamaha USA, moves the RMax unmanned helicopter into position before a demonstration of its aerial application capabilities at the University of California, Davis' Oakville Station test vineyard in Oakville, Calif. Researchers at UC Davis have been studying the effectiveness of the drone's ability for spraying pest control and nutritional materials on the test vineyard in California's Napa Valley. (Photo by Rich Pedroncelli/AP Photo)